2.1.2. Secoiridoids

Secoiridoids are produced from the secondary metabolism of terpenes. These compounds are characterized by the presence of elenolic acid or its derivates in its glycosidic or aglyconic form in their molecular structure [12]. As reported in Table 1, secoiridoids that could be identified in the different extracts included free forms such as secologanoside (peak 1, *m/z* 389.1089) and loganoside (peak 1, *m/z* 389.1447), as well as phenol-conjugated secoiridoids in glycosidic form such as oleuropein (peaks 9 and 10, *m/z* 539.177) and ligstroside (peak 11, *m*/*z* 523.1821). Such compounds have been reported in olive leaves and other organs of the olive tree in previous literature [13–16].
